This randomized phase III trial studies olaparib or cediranib maleate and olaparib to see how well they work compared with standard platinum-based chemotherapy in treating patients with platinum-sensitive ovarian, fallopian tube, or primary peritoneal cancer that has come back. Olaparib and cediranib maleate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Cediranib maleate may stop the growth of ovarian, fallopian tube, or primary peritoneal cancer by blocking the growth of new blood vessels necessary for tumor growth. Drugs used in chemotherapy, such as carboplatin, paclitaxel, gemcitabine hydrochloride, and pegylated liposomal doxorubicin hydrochloride work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. It is not yet known whether olaparib or cediranib maleate and olaparib is more effective than standard platinum-based chemotherapy in treating patients with platinum-sensitive ovarian, fallopian tube, or primary peritoneal cancer.

This randomized phase II/III trial studies how well paclitaxel, carboplatin, and metformin hydrochloride works and compares it to paclitaxel, carboplatin, and placebo in treating patients with endometrial cancer that is stage III, IV, or has come back. Drugs used in chemotherapy, such as paclitaxel and carboplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Metformin hydrochloride may help paclitaxel and carboplatin work better by making cancer cells more sensitive to the drugs. It is not yet known whether paclitaxel and carboplatin is more effective with or without metformin hydrochloride in treating endometrial cancer.